Absolutes can be indispensable when learning. An entire concept can be boiled down to black-and-white, and often can be completely forgotten about while a learner groks the rest of a subject. Part of the path to expertise for a learner is to go back and challenge those absolutes, because those absolutes are now part of the learner's assumptions.

When people espouse absolutes, I generally (not absolutely) assume either they're not experts or they think their audience can't handle nuance.